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    <script>
        const g = {b:3}
        console.log(g.b)//3
        g.b = 12;
        console.log(g.b)//12

        let [head,...tail] = [1,2,3,4]
        console.log(tail)// [2,3,4]
        console.log("2"+3+4)//234

        function foo(){
            console.log("first")
            setTimeout(() => {
                console.log("second")
            }, 5);
        }
        for (var i = 0;i<43999;i++){foo()}
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